Production of composite materials

ABSTRACT

A bearing material comprising a metal matrix reinforced with less than 50 percent by volume fibres is disclosed. Preferably the fibres comprise 10 to 25 percent by volume of the bearing material and may be carbon or asbestos fibres whilst the matrix may be lead, a lead/tin alloy or silver. The bearing material may be provided with a steel backing strip to form a thin wall bearing component.

United States Patent [1 1 Dec.4, 1973 Barlow PRODUCTION OF COMPOSITE3,491,055 1/1970 Talley 161/170 M ATERIALS 3,572,971 3/1971 Seiwert..416/230 3,575,783 4/1971 Kreider 161/207 [75] Invent r: J h a hall,England 3,616,300 10/1971 Ahmad 161 170 Assigneez GJQNLGmup servicesLinited 3,616,508 11/1971 Wallett 29/l56.8 R

Smethwick, Warley, England [22] Filed: July 22, 1971 PrimaryExaminer-William J. Van Balen 1 pp No: 165,303 Attorney Ho man & Stem[30] Foreign Application Priority Data July 29, 1970 Great Britain36,652 70 [57] ABSTRACT Sept. 22, 1970 Great Britain 44,972/70 A bearingmaterial comprising a metal matrix rein- 52 U.S. c1 308/238, 308/237,161/170, forced with less that 50 Percent y volume fibres is disclosed.Preferably the fibres comprise 10 to 25 per- 51 1m. 01. F166 27/00 centby volume of the bearing material and y be [58] Field of Search 161/168,170, 205, carbon or asbestos fibres whilst the matrix y be 161/175, 176,172, 42; 308/237, 23 lead, a lead/tin alloy or s1lver.

The bearing material may be provided with a steel [56] References Citedbacking strip to form a thin wall bearing component.

UNlTED STATES PATENTS 7/1969 Alexander et a1. 29/ 191.4

9 Claims, 1 Drawing Figure PRODUCTION OF COMPOSITE MATERIALS BACKGROUNDOF THE INVENTION 1. Field of the Invention This invention relates to abearing material, comprising a metal matrix reinforced by fibres.

2. Description of the Prior Art Hitherto a bearing material of the typedescribed above generally included 50 percent or even more by volume offibres and the bearing surface of a bearing component made out of thebearing material has been at least mainly constituted by the fibreswhilst the metal matrix has constituted a binder for the fibres.

SUMMARY OF THE INVENTION An object of the present invention is toprovide a new and improved bearing material of the type described above.

According to one aspect of the present invention we provide a bearingmaterial comprising a metal matrix reinforced with fibres, the fibrescomprising less than 50 percent by volume of the bearing material, andwherein the fibres are at least substantially completely embedded in andcovered by the matrix; whereby at least no substantial amount of fibresare present at the surface of a bearing component made from the bearingmaterial.

The fibres may comprise to 25 percent by volume of the bearing material.

The fibres may be carbon fibres or asbestos fibres.

The fibres may be in the form of flock, i.e. fibres of relatively shortlength, for example, fibres having a maximum dimension of about 0.5inches.

Alternatively the fibres may be relatively long fibres. For example,long carbon fibres are commercially available in tows commonly havingabout 10,000 fibres for each tow and the fibres being about 4 feet long.In use, in the present application, fibres of a suitable length are cutfrom the tow.

The maxtrix may be lead, a lead/tin alloy, or'silver.

The bearing material may be provided with a steel backing strip to forma thin wall bearing component.

BRIEF DESCRIPTION OF THE DRAWINGS The drawing is a diagrammatic planview of an electrode assembly of a plating bath used in a method ofmaking the composite material embodying the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS A bearing material embodying thepresent invention will now be described in more detail by way ofexample.

In this example the bearing material comprises a matrix of leadreinforced with carbon fibres.

The carbon fibres comprise 10 percent by volume of the compositematerial, and the fibres are completely embedded in and covered by thematrix so that the fibrous material is not anywhere exposed at a surfaceof the bearing material. Thus, when the bearing material is made into abearing component the load carrying surface of the bearing isconstituted solely by the matrix material and the fibres are not at allcontacted by a member supported in the bearing.

The bearing material of the present invention may be used in any desiredform of plan bearing. One form of bearing is a thin wall type bearing inwhich the bearing material is provided with a thin steel backing memberof semi-cylindrical half shell or of bush shape.

The backing member is of conventional form being made of steel with ahot dipped tin coating.

Thecomposite material may be bonded to the backing strip in any desiredway.

For example, the bearing material may be placed in a die with thebacking strip and hot pressed to the desired final shape of the bearingcomponent and at the same time caused to bond to the backing strip.

Or, preferably, by hot pressing the bearing material onto the backingstrip to make a flat laminate and then warm bending to laminate tohalf-shell or bush shape.

Although the particular case of a bearing material comprising a leadmatrix with 10 percent by volume carbon fibres has been describedhereinbefore, if desired the bearing material may have between about 5to 50 percent fibre by volume and preferably between 10 and 25 percent.Instead of carbon fibres, asbestos fibres may be used and the matrix maycomprise silver or a lead/tin alloy instead of lead.

Furthermore, whilst it is preferred that the fibres are completelyembedded in the matrix, a satisfactory bearing is obtained so long as nosubstantial amount of fibres are present at the surface.

The fibres in the bearing material may be flock fibre material or longfibre material.

Two methods of making a composite material for use as a bearing materialwill now be described with reference to the accompanying drawing.

A plating solution was prepared from the following ingredients 23 mls ofa stannous fluoroborate solution having a specific gravity of 1.46 andcontaining 300 grams per litre of tin,

mls. of lead fluoroborate solution having a specific gravity of 1.80 anda lead content of 520 grams per litre,

36 mls of fluoroborate acid,

25 grams of boric acid,

0.5 grams of glue or gelatin and 1 gram of resorcinol and water to 1litre.

The above plating solution was such that with a current density of 30amps per square foot, a plated coating was obtained containing 7 percentby weight tin and 93 percent by weight lead.

As shown in the drawing, the plating bath contained an inner anode 10which was set into the base of the bath and an outer anode assembly 1 lwhich comprised four anode plates spaced about the inner anode 10. Acathode assembly comprising a plurality of cathode rods 12 was suspendedfrom a supporting plate 13 of insulating material and a motor (notshown) was provided for rotating the plate 13 and thus the cathode rods12 about a vertical axis 14 which passes through the centre of the inneranode 10. The radial spacing between the cathoderods 12 and the inneranode 10 was substantially the same as the radial spacing between theouter anodes 11 and the cathode rods 12.

The cathode rods 12 were steel rods which were partially covered by aninsulating material so that each rod included a 2 cm length portion incontact with the electrolyte in the bath which was as set out above.

The motor for rotating the supporting plate 13 was arranged to rotatethe cathode rods 12 about the axis 14 at a rate of the order of 30 to 60rpm. A suspension of carbon fibres in water was added to the platingbath with the cathode rods 12 rotating about the axis 14 and with astirrer provided for maintaining the carbon fibres in suspension. Thecarbon fibres migrated to the cathode rods and projected therefromrather as if they were branches of a fir tree.

Plating was carried out for an hour with a current density of 30 ampsper square foot, the area of the cathode being considered as includingthe surface area of the cathode rods plus the surface area of the carbonfibres added. Thus, when 015 grams of carbon fibres had been added, thesurface area of the carbon fibres was of the order of 70 square incheswhich was considerably greater than the surface area of the portions ofthe steel rods of the cathode assembly which are not insulated. Themajor proportion, therefore, of the lead/- tin alloy which is platedinto the cathode assembly is plated onto the carbon fibres.

By arranging for there to be an inner anode l and an outer anodeassembly 11, with the cathode rods 12 disposed substantiallyequi-distant from the inner anode l0 and the outer anode assembly 11, asubstantially uniform distribution of carbon fibres on each cathode rodwas obtained, this was also assisted by rotating the cathode rods aboutthe axis 14. The carbon fibres added were of short length, their lengthsbeing of the order of 0.1 inches to 0.125 inches and plating of thelead/tin alloy was continued until the volume of lead/tin alloy platedonto the carbon fibres was of the order of nine times the volume of thecarbon fibres.

The cathode rods were removed from the plating path and the platedcarbon fibres were then scrapped off the cathode rods.

A consolidation operation was then carried out in a press, the pressingbeing carried out within the temperature range of from 200 to 280C witha pressure of from 20 tons per square inch to tons per square inch. Thepressure applied to consolidate the plated fibrous material depends onthe temperature at which the pressing operation is carried out, thehigher the pressing temperature the lower may be the applied pressure.

In the example described above the temperature was 220C and the pressurewas tons per square inch.

A sample of the material of the above example was subjected to a punchshear test.

This test provides a means for assessing the ultimate strength of thematerial subjected to shear loading. The test is carried out on aHounsfield tensometer and a steel punch is forced through a disc of thematerial and the maximum load (p) is recorded. The shear strength (S) isthen obtained from the formula Punch Shear Strength /m m) TheoreticalDensity Material Lead/tin alloy (93/7) 26 (Chill cast) Lead/tin alloy(93/7) l0 vol. shot carbon fibres 98 76.4

The punch shear strengths provided in the table are the mean of 10results for each material.

The bearing material may be made by methods other than those describedabove.

In the case of long carbon fibres, the bearing material may be made byelectro plating the matrix material, for example, lead, onto long carbonfibres arranged in substantially spaced parallel relation on a cathodeframe of the electrolytic bath, followed by consolidation ashereinbefore described.

I claim:

1. A bearing material comprising a bearing metal matrix, a plurality ofinorganic fibres in the form of flock embedded directly in said matrixto reinforce said matrix, said fibres comprising less than 50 percent byvolume of the bearing material and being randomly orientated in thematrix, and the metal matrix providing a bearing surface portion of thebearing material and there being at least no substantial amount of thefibres present at said bearing surface.

2. A bearing material according to claim 1 wherein the fibres comprise10 to 25 percent by volume of the bearing material.

3. A bearing material according to claim 1 wherein the fibres are carbonfibres.

4. A bearing material according to claim 1 wherein the fibres areasbestos fibres.

5. A bearing material according to claim 1 wherein the fibres compriserelatively long carbon fibres.

6. A bearing material according to claim 1 wherein the fibres arearranged in a desired orientation.

7. A bearing material according to claim 1 wherein the bearing materialis provided with a backing strip to form a thin wall bearing component.

8. A bearing comprising two components having bearing surfaces insliding contact with each other, one of said components comprising abearing material comprising a bearing metal matrix, a plurality offibres in the form of flock embedded directly in said matrix toreinforce said matrix, said fibres comprising less than 50 percent byvolume of bearing material and being randomly orientated in the matrix,and the metal matrix providing said bearing surface of the bearingmaterial, and there being at least no substantial amount of fibrespresent at said bearing surface.'

9. A thin wall bearing component comprising a metal backing member, abearing metal matrix, bonded to said backing member, a plurality offibres in the form of flock embedded directly in said matrix toreinforce said matrix, said fibres comprising less than 50% by volume ofthe bearing material and being randomly orientated in the matrix, andthe metal matrix providing a bearing surface portion of the bearingmaterial and there being at least no substantial amount of the fibrespresent at said bearing surface.

2. A bearing material according to claim 1 wherein the fibres comprise10 to 25 percent by volume of the bearing material.
 3. A bearingmaterial according to claim 1 wherein the fibres are carbon fibres.
 4. Abearing material according to claim 1 wherein the fibres are asbestosfibres.
 5. A bearing material acCording to claim 1 wherein the fibrescomprise relatively long carbon fibres.
 6. A bearing material accordingto claim 1 wherein the fibres are arranged in a desired orientation. 7.A bearing material according to claim 1 wherein the bearing material isprovided with a backing strip to form a thin wall bearing component. 8.A bearing comprising two components having bearing surfaces in slidingcontact with each other, one of said components comprising a bearingmaterial comprising a bearing metal matrix, a plurality of fibres in theform of flock embedded directly in said matrix to reinforce said matrix,said fibres comprising less than 50 percent by volume of bearingmaterial and being randomly orientated in the matrix, and the metalmatrix providing said bearing surface of the bearing material, and therebeing at least no substantial amount of fibres present at said bearingsurface.
 9. A thin wall bearing component comprising a metal backingmember, a bearing metal matrix, bonded to said backing member, aplurality of fibres in the form of flock embedded directly in saidmatrix to reinforce said matrix, said fibres comprising less than 50% byvolume of the bearing material and being randomly orientated in thematrix, and the metal matrix providing a bearing surface portion of thebearing material and there being at least no substantial amount of thefibres present at said bearing surface.